The present invention relates to an FRP rod material used as a building material, e.g., a reinforcing bar in place of steel rods.
So called FRP (Fiber-Reinforced Plastic) has been in widespread use in a variety of construction materials because it has a high specific strength, good anticorrosion properites, excellent moldability, shape workability, and the like. For example, if FRP rods are used as reinforcing bars in place of steel rods, the reinforcing bars are prevented from being corroded by salt improving the durability of the building. In addition, FRP rods are lightweight, and thus easy to handle at a construction site.
In the prior art, Takahasi, et al., U.S. patent application Ser. No. 06/849,856 entitled "REINFORCING MEMBER HAVING A PROJECTION ON ITS SURFACE", filed on Apr. 9, 1986 discloses a reinforcing member as a substitute for a steel bar, having a synthetic resin core and projections on the surface of the core. This core is a FRP rod having a bundle of continuous fibers, such as rovings, and a synthetic resin bonding the fibers together to form the core.
However, conventional FRP rods like the reinforcing member in Takahashi et al. do not have so-called "toughness". In other words, they are substantially free from the plastic deformation generally found in steel rods. Therefore, the application field of conventional FRP rods is limited to applications which do not require material toughness.